Various schemes for storing data magnetically are known that permit the stored data to be recalled conveniently for use. For example, recording sounds and/or images on magnetic tape, comprising a thin, flexible, ribbon-like substrate coated with a magnetic medium, is well known and has been used for years. The sound or image data can be stored in analog form or digital (binary) form. The recorded data is read off the tape using an appropriate “reader.” Another major use of magnetic data storage is floppy disks and hard disks used with virtually every laptop or larger computer currently in use. These devices normally store data in digital binary form.
The general concept of storing data magnetically is also used in most, if not all, transactions involving credit cards, debit cards, identity cards, passcards, phone cards, transportation tickets, and the like. Many types of such cards and analogous devices include one or more strips of magnetic data-storage medium that can be read and processed as required in the course of the transaction. This form of data storage is aimed at providing some degree of security of the transaction, and also greatly increases the speed and number of transactions that an be executed, per unit time.
Yet another form of magnetically based data storage is the use of magnetic “inks” on transactional and commercial documents such as bank checks, deposit slips, securities, order sheets, and the like. For example, account numbers and other information typically is printed along the bottom margin of bank checks using a type of magnetic ink and a particular font. Some consideration has been given to using analogous inks on currency as an anti-counterfeiting measure. In this latter regard, use of magnetic-based compositions has been combined with other techniques such as diffractive techniques. An example of this is discussed in U.S. Pat. No. 6,902,807 to Argoitia, incorporated herein by reference.
A disadvantage of these various conventional magnetically based data-storage techniques is that the data-storage capacity is limited, at least in part, as a result of the data being stored in binary form. At a particular locus in a binary data-storage device, a data bit is stored as one of two possible states, namely “0” or “1”. Consequently, storing binary data requires a large amount of data-storage space. Another disadvantage is that the resolution of data storage and recall is limited in these devices largely by the devices' two-dimensional configurations.
Another disadvantage is the ease in which the data can be destroyed or at least corrupted, accidentally or deliberately. For example, passage of a credit card or debit card over or through a strong magnetic field can erase or change some or all the information on the card's magnetic strip.
Another disadvantage of conventional data-storage techniques is the vulnerability of the data to theft or unscrupulous use. Theft simply requires the thief to have a magnetic reader, and the thief need not have possession of the data-storage device any longer than the instant during which the device is being covertly read.
Hence, there remains a need for improved data-storage devices and methods.